Create a section that specifies how to deal with DRM device resets for kernel and userspace drivers. Signed-off-by: André Almeida <andrealmeid@xxxxxxxxxx> --- Documentation/gpu/drm-uapi.rst | 51 ++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst index 65fb3036a580..3d6c3ed392ea 100644 --- a/Documentation/gpu/drm-uapi.rst +++ b/Documentation/gpu/drm-uapi.rst @@ -285,6 +285,57 @@ for GPU1 and GPU2 from different vendors, and a third handler for mmapped regular files. Threads cause additional pain with signal handling as well. +Device reset +============ + +The GPU stack is really complex and is prone to errors, from hardware bugs, +faulty applications and everything in the many layers in between. To recover +from this kind of state, sometimes is needed to reset the GPU. Unproper handling +of GPU resets can lead to an unstable userspace. This section describes what's +the expected behaviour from DRM drivers to do in those situations, from usermode +drivers and compositors as well. The end goal is to have a seamless experience +as possible, either the stack being able to recover itself or resetting to a new +stable state. + +Robustness +---------- + +First of all, application robust APIs, when available, should be used. This +allows the application to correctly recover and continue to run after a reset. +Apps that doesn't use this should be promptly killed when the kernel driver +detects that it's in broken state. Specifically guidelines for some APIs: + +- OpenGL: KMD signals the abortion of submitted commands and the UMD should then + react accordingly and abort the application. + +- Vulkan: Assumes that every app is able to deal with ``VK_ERROR_DEVICE_LOST``. + If it doesn't do it right, it's considered a broken application and UMD will + deal with it, aborting it. + +Kernel mode driver +------------------ + +The KMD must be able to detect that something is wrong with the application +and that a reset is needed to take place to recover the device (e.g. an endless +wait). It needs to properly track the context that is broken and mark it as +dead, so any other syscalls to that context should be further rejected. The +other contexts should be preserved when possible, avoid crashing the rest of +userspace. KMD can ban a file descriptor that keeps causing resets, as it's +likely in a broken loop. + +User mode driver +---------------- + +During a reset, UMD should be aware that rejected syscalls indicates that the +context is broken and for robust apps the recovery should happen for the +context. Non-robust apps must be terminated. + +Compositors +----------- + +Compositors should be robust as well to properly deal with its errors. + + .. _drm_driver_ioctl: IOCTL Support on Device Nodes -- 2.39.2
